1. Field of the Invention
The present invention relates to flow line closures or connectors for sealingly connecting tubular members which are pivoted or misaligned with respect to each other.
2. Background
In the field of fluid handling, such as for example in marine pipelines, there have been developed a number of connection or closure arrangements for connecting flow tubes or conduits. In certain applications, such connectors must seal adjoining tubular members which are misaligned, or in other words, such members are not generally coaxial and may need to be joined at a slight angle relative to each other. Such connectors are often referred to as misaligning flanges, ball connectors, and swivel couplings, to name a few.
These known ball connectors generally have a first tubular member with an annular convex sealing surface and a second tubular member with an annular concave sealing surface. The sealing surfaces are generally drawn together by opposed flanges on each tubular member which are bolted together to form a seal, typically with an O-ring or gasket disposed therebetween. One or both of the flanges is typically pivotable with respect to the tubular member on which it is mounted. The concave and convex sealing surfaces are typically spherically shaped to permit the tubular members to be swiveled or pivoted so that the tubular members can be sealingly connected without coaxial alignment. Such an arrangement is particularly advantageous in subsea or marine environments where pipelines cannot be laid substantially in alignment, or where it may become necessary to repair portions of the pipeline which have been displaced by ship anchors, for example, or other forces.
One problem with such conventional swivel couplings is that the tubular members may need to be axially displaced to draw the sealing surfaces of the swivel coupling into engagement. As a result, it is often difficult to establish the proper torque loadings on the flange bolts since some of the loading is necessary to draw or hold the tubular members themselves, in addition to that required to compress a sealing element between the concave-convex sealing surfaces to effect a fluid-tight seal therebetween. As a consequence, a leak may form because of the uneven or non-uniform compression of the sealing element.
Another problem with such swivel couplings heretofore used is that forces imparted to the adjacent tubular members after installation of the coupling tend to induce a bending moment at the joint which may also cause pivoting or swiveling of the adjoining tubular members connected thereby and eventual leaking of the seal due to damage to the sealing element caused by movement thereof on the sealing surface and/or uneven compression of the sealing element.
One attempt at overcoming these problems is the fluid actuated pipe connection described in U.S. Pat. No. 3,874,706. In this connector, the female portion of the coupling element is provided with a separate hydraulic actuated cam member for locking the coupling, in addition to a hydraulically actuated O-ring for effecting a fluid seal between the male and female members of the connection.
Another attempt at overcoming these problems is the swivel coupling element described in U.S. Pat. Nos. 4,381,871 and 4,618,173. The swivel coupling element disclosed therein includes an annular mounting flange having a leading end for seating on a seating face of a conventional flange and a trailing end in which an annular concave spherical surface is formed. This coupling also includes a tubular member having an end with a complementary convex annular spherical surface to cooperate with the concave surface of the mounting flange, and an annular flange for securing the conventional flange to the flange of the male tubular member with the sealing flange positioned therebetween. The concave-convex sealing surfaces of this coupling are sealed by a metal O-ring placed in an annular recess formed in either or both of the sealing surfaces. To ensure proper compression of the O-ring gasket, the male member annular flange is separately bolted to the mounting flange with a separate set of bolts prior to bolting the assembly to the conventional flange. Since the male member in this arrangement is otherwise free to pivot with respect to its annular flange, the male member is locked into position with respect to the annular flange by the provision of corresponding opposed roughened surfaces formed on respective trailing surfaces thereof.
A disadvantage of such prior art connections is the complexity of manufacture and installation, and a large number of parts needed to effect the closure. This tends to add greatly to the manufacturing and installation costs thereof, and also to multiply the sources for failure and leakage.
Accordingly, there is a need for a swivel flow line connector having simplicity of manufacture and installation, which properly seats a sealing element regardless of the forces required to position the adjacent tubular members thereof, and which resists pivoting or swiveling following connection which might consequently damage the sealing element.